As is well known, various liquids are contaminated by organic materials. For example, used lubricating oil frequently includes organic materials comprising products of combustion. Waste water is almost always contaminated by organic materials such as human and animal waste, decaying vegetable materials, etc.
As is also well known, organic contaminants can be removed from liquids by exposing the contaminated liquids to oxidizing agents, particularly oxidizing gases. Ozone and chlorine dioxide are among the most potent of the oxidizing gases, and therefore offer tremendous potential with respect to the removal of organic contaminants from used lubricating oil, wastewater, and other liquids. Unfortunately, the inherent instability of ozone and chlorine dioxide has heretofore limited the efficient commercial utilization thereof in the removal of organic contaminants from liquids.
Another problem involved in the removal of organic contaminants from liquids is the time duration of the exposure of an oxidizing agent to the contaminants in the liquid. As is known from Stoke's Law, larger bubbles rise faster in a given liquid. Because it has heretofore not been possible to generate sub-micron size bubbles of oxidizing gases, much larger bubbles, bubbles in the 100-500 micron range, have necessarily been used. Due to the relatively rapid movement of larger bubbles, towers having substantial vertical height have been required in order to increase the time duration of the exposure of the oxidizing gas to the contaminated liquid. Unfortunately, increasing height of the tower increases the pressure that is necessary to overcome head pressure in order to disperse the oxidizing gas in the liquid to be treated.
Organic contaminants can also be removed from liquids by means of oxidizing liquids such as hydrogen peroxide. Oxidizing liquids are typically quite expensive relative to oxidizing gases. For this reason it has heretofore been impractical to utilize oxidizing liquids in wastewater treatment and similar large scale operations.
The present invention comprises a method of and apparatus for utilizing oxidizing gases and oxidizing liquids to remove organic contaminants from liquids which overcomes the foregoing and other problems long since associated with the prior art. In accordance with one aspect of the invention, oxidizing gas is utilized at its source and is formed into sub-micron size bubbles which are immediately dispersed into a flowing liquid to be decontaminated. Due to the sub-micron size of the bubbles, the surface area of the oxidizing gas is greatly increased, thereby greatly increasing the efficiency of the gas in oxidizing organic contaminants from the liquid. This in turn substantially reduces the vertical height necessary to effectively treat the contaminated liquid, thereby substantially reducing the pressure at which the oxidizing gas is used.
In accordance with a first application of the invention, an oxidizing gas is selected from the group including ozone and chlorine dioxide. The oxidizing gas is formed into sub-micron size bubbles by directing it through a sintered stainless steel, sintered glass, sintered ceramic, or porous ceramic tube. Used lubricating oil is caused to flow past the exterior of the sintered/porous tube. The flowing liquid cleaves sub-micron size bubbles of the oxidizing gas from the surface of the tube. The sub-micron size bubbles of oxidizing gas are dispersed into the used lubricating oil, whereupon organic contaminants contained within the used lubricating oil are efficiently oxidized.
In accordance with a second application of the invention, an oxidizing gas is selected from the group including ozone and chlorine dioxide. The oxidizing gas is formed into sub-micron sized bubbles by directing it through a sintered stainless steel, sintered glass, sintered ceramic, or porous ceramic tube. Wastewater is caused to flow past the exterior of the tube. The flowing liquid cleaves sub-micron size bubbles of the oxidizing gas from the surface of the tube. The sub-micron size bubbles of oxidizing gas are dispersed into the wastewater, whereupon organic contaminants contained within the wastewater are efficiently oxidized.
In accordance with a second aspect of the invention, the exterior surface of the sintered stainless steel, sintered glass, sintered ceramic or porous ceramic tube is provided with a coating of a radiation-activated catalyst such as titanium dioxide. During operation, the catalyst is activated by exposure by ultraviolet radiation, sunlight, visible light, or other electromagnetic radiation. Activation of the catalyst causes the formation of hydroxyl radicals in the contaminated liquid which augment the action of an oxidizing gas or an oxidizing liquid in the removal of organic contaminants from the liquid.